The present application is related to the co-filed U.S. application Ser. No. 13/789,682 entitled “Frequency Pulling Reduction in Wide-Band Direct Conversion Transmitters” filed on Mar. 8, 2013, which is assigned to the same assignee as the present application and incorporated herein by reference in its entirety.
The Federal Communications Commission (FCC) has allotted a spectrum of bandwidth in the 60 GHz frequency range (57 to 64 GHz). The Wireless Gigabit Alliance (WiGig) targets the standardization of this frequency band that will support data transmission rates up to 7 Gbps. Integrated circuits, formed in semiconductor die, offer high frequency operation in this millimeter wavelength range of frequencies. Some of these integrated circuits utilize Complementary Metal Oxide Semiconductor (CMOS), Silicon-Germanium (SiGe) or GaAs (Gallium Arsenide) technology to form the dice in these designs.
CMOS (Complementary Metal Oxide Semiconductor) is the primary technology used to construct integrated circuits. N-channel transistors and P-channel transistors (MOS transistor) are used in this technology which uses fine line technology to consistently reduce the channel length of the MOS transistors. Current channel length examples are 40 nm, the power supply of VDD equals 1.2V and the number of layers of metal levels can be 8 or more. This technology scales and can achieve operation in the 60 GHz range.
Transceivers for the 60 GHz system have been formed in CMOS and comprise at least one transmitter and at least one receiver which are used to interface to other transceivers in a communication system. The transceivers receive or transmit electrical signals into the LNA or the power amplifier, respectively. These electrical signals are generated by or provided to an antenna. The antenna is a transducer that converts incoming electromagnetic energy from free space into electrical signals on the receive side of the transceiver or converts electrical signals into electromagnetic energy for transfer into free space.
The transmitter needs to provide a signal to the antenna consisting of a 60 GHz carrier frequency range. The Gilbert mixer plays a fundamental role in up-converting a baseband signal to this carrier frequency range. Binary Phase Shift Keying (BPSK) is the modulation scheme used to carry the baseband at the 60 GHz carrier frequency range. The Gilbert mixer also plays a fundamental role in down-converting a Radio Frequency (RF) signal to baseband.
The Gilbert mixer mixes a local oscillator signal at a given frequency with a baseband signal. The oscillator signal typically has a full rail to rail voltage swing and can be viewed as a “square wave” applied to the gates of the transistors in the Gilbert mixer. These gates then act like switches that become enabled and disabled in sequential order. The reduced swing from the baseband, however, has only a limited swing of 300 mV and must be of sufficient magnitude to place the drive the gates of the driven transistors into saturation.
One type of transistor used in the Gilbert mixer is an N-Metal Oxide Semiconductor (NMOS) transistors, although these gates can also be P-Metal Oxide Semiconductor (PMOS) transistors. Both of these types of transistors are used in the Complementary Metal Oxide Semiconductor (CMOS) technology. In addition, any technology of transistors can be used for the Gilbert mixer; bipolar, hetro-junction, etc.